Cleaning Head

ABSTRACT

When, according to the invention, a cleaning head is provided with a hysteresis coupling ( 9, 11 ) between the turbine ( 3 ) and the gear in the gear housing ( 13 ), the gear will remain separated from the turbine and not be subjected to liquid impact. The hysteresis coupling ( 9, 11 ) may be adjusted using electromagnets ( 9 ) as an inductor, which allows control/regulation of the rotating movements of the cleaning head to achieve the best possible cleaning pattern.

THE PRIOR ART

The invention relates to a cleaning head, in particular for mountinginside a tank, said head being provided with a turbine which is drivenby a source of pressure liquid for causing rotation of a gear, which inturn causes the gear housing and a hub, mounted thereon and havingnozzles, to rotate, said liquid being conveyed from the turbine and tothe nozzles in operation, said gear housing being mounted on astationary mounting part so that the liquid from the turbine bypassesthe gear housing and flows to the nozzles, and that the rotation of theturbine is transferred to the input shaft of the gear by means of amagnetic coupling having coupling parts, the driving coupling part ofwhich being disposed outside the gear housing, and the driven couplingpart of which being disposed inside the gear housing.

Cleaning equipment of this type is used in particular for the cleaningof tanks, it being possible to eject cleaning jets by means of nozzlesand pressure liquid which will clean the tank in an effective manner bytheir combined turning and rotation.

The rotation produced by the turbine is transferred to a gear whichpartly turns the housing, partly rotates the rotary hub with thenozzles. Hereby, the liquid is passed through the gear and further outto the nozzles.

If there is a need for separating the liquid part from the gear,transfer of the rotation of the turbine to the gear may take place via amagnetic coupling, as the driving magnetic part is disposed outside thehousing, while the gear is incorporated in a closed housing separatedfrom the liquid, and with the driven magnetic part connected with theinput shaft of the gear.

Such a cleaning head for a tank cleaning system is known from U.S. Pat.No. 5,871,023, in which it may be seen in FIG. 2 that the impeller 38 inthe liquid channel drives a disc-shaped magnetic part 40, which isdisposed outside the gear housing, and which is coupled magnetically toanother disc-shaped magnetic part 58, which is located “dry” inside thegear housing. It is described in column 4, lines 33-38 and column, lines4-10 that each of the magnetic parts consists of four uniform magnetswhich are embedded in a disc of stainless steel, and that the magnetsare of materials which are typically used for the manufacture ofpermanent magnets.

In practice, however, it is difficult to make such a magnetic couplinghaving permanent magnets on the driving side as well as the driven sidework satisfactorily in connection with cleaning heads for tanks.

The problem of this known coupling head is the risk of missing magneticcoupling-together and thus missing transfer of the rotary movement, justas there is a great risk of “slip” in the coupling. The latter isprimarily due to the high speed of rotation which is imparted to theturbine at start, which results in difficulties in capturing the fieldbecause of the high speed of rotation and the stationary, driven part.

Such a situation occurs when the starting torque or the load torqueexceeds the maximum torque of the coupling. The coupling slips in ajerky or shaking manner, because the magnetic forces are interruptedbetween the poles disposed opposite each other and can then onlytransfer very small torques. Therefore, it is necessary to close downthe system completely in order to avoid damage to bearings and otherparts in the system.

Couplings of this type having permanent magnets are also calledsynchronous couplings for the same reason, precisely because it is arequirement for a satisfactory function that the coupling parts movetogether. In other words, it is necessary to dimension the coupling suchthat its maximum torque is considerably greater than the starting torqueif the system is to be able to start. However, the situation mightalways occur that errors or impurities in the liquid flow may cause theload torque to exceed the maximum torque that can be transferred, whichcauses slip in the coupling. Under normal conditions of operation, thesecouplings operate with a fixed slip angle which is determined in thedimensioning.

THE OBJECT OF THE INVENTION

The object of the invention is to remedy these defects and drawbacks,and this is achieved according to the invention by a cleaning head,wherein the rotation of the turbine is transferred to the gear in thegear housing via a hysteresis coupling comprising a magnetic inductor inthe liquid space which is driven by the turbine, and which drives ahysteresis part which is mounted in the gear housing, and which isconnected with the input shaft of the gear.

Such a hysteresis coupling provides for an unprecedented possibility ofensuring a quite certain torque transfer of the rotating movement at thestart phase for cleaning heads for tanks. It has surprisingly been foundthat in spite of the great difference in the speed of rotation at themoment of start between the driving and the driven magnetic parts, thehysteresis coupling is capable of supplying a torque which issufficiently great to accelerate the driven magnetic part and therebythe gear in terms of speed, if it is dimensioned correctly, that is thatit can transfer a torque which is greater than the starting torque.

The advantageous properties of the hysteresis coupling includeadditionally that it is able to transfer an almost constant torqueindependently of the relative speed between the coupling parts, and thatthe coupling is able to operate with a continuous or varying slip, andthat this slip is “soft” and has no detrimental effect on the structure.

In situations of slip, however, energy from the driving magnetic partaccumulates in the material of the hysteresis part, because the poles inthe hysteresis part constantly move at the passage of the poles of theinductor. This energy is transformed into heat, which is discharged tothe surroundings via the pressure liquid.

When, as stated in claims 2 and 3, electromagnets are used as aninductor, it is possible to adjust the field strength and thereby tovary and control the slip and thus the transferred torque and/or thespeed.

When, as stated in claim 4, permanent magnets are used as an inductor,it is possible to produce an inexpensive coupling which ismaintenance-free, and which may be used inter alia in environments withinflammable and explosive vapours.

THE DRAWING

An example of an embodiment of a cleaning head according to theinvention will be described more fully below with reference to thedrawing, which shows a partially sectional view of a cleaning head.

DESCRIPTION OF AN EXEMPLARY EMBODIMENT

As shown in the drawing, the cleaning head comprises an inlet stub and astationary part 6 to which a pipe (not shown) may be secured, andthrough which cleaning liquid may be supplied to the cleaning head.

The inlet channel 1 conveys the liquid through a stator 2 having guideplates to a turbine 3 having propellers, and both are mounted in theliquid space in the stationary part 6 of the cleaning head.

The turbine 3 is connected with the turbine shaft, which is connectedwith the driving inductor part 9 of the hysteresis coupling, which isalso present in the liquid space.

The driving inductor part 9 is preferably composed of a plurality ofelectromagnets, which have the advantage that the magnetic fieldstrength may be varied steplessly by changing the voltage. This providesthe option of adjusting the slip and thereby the torque and/or the speedwhich it is desired to transfer via the coupling.

Instead of electromagnets, the inductor part 9 may be equipped withpermanent magnets. This results in a coupling which, however, cannot beregulated, but which is easy and inexpensive to manufacture, and whichis intended for use in tank cleaning systems which involve working withliquids that release vapours which are inflammable or explosive.

The gear housing 13 is mounted below the stationary part 6 such thatliquid-wise the housing is separated by a partition 10 from the liquidspace and the liquid flow in the channel 5, and, in the other words,that the gear is separated from the liquid.

The driven part 11 of the hysteresis coupling is mounted and secured tothe input shaft 12 of the gear inside the gear housing 13. Preferably,the driven part 11 is made of a magnetic material containing metaloxides, such as Fe 203 powder which is electrically insulating. Thismaterial has a high isotropic electrical resistance, which effectivelyprevents the generation of eddy currents in the hysteresis part.Further, the magnetic properties are good, even at relatively hightemperatures.

Instead of this embodiment, it is conceivable to use a laminatedmaterial having layers of a ferromagnetic hysteresis material, which isinsulated from each other by means of dielectric films.

The gear drives the gear housing 13 and the nozzle hub 15 to turn androtate, respectively, so that, via the channels 4 and 5, the liquid maybe conveyed to the nozzles 14 through channels 7 and flow out throughnozzle openings 8.

If the inductive part 9 of the hysteresis coupling is provided withelectromagnets, it is possible to regulate the slip by adjustment of thefield strength and thereby the torque transferred by the coupling and/orthe speed, which provides the desired turning and rotating movement.

Hereby a cleaning pattern may be achieved electronically, i.e. a controlof the cleaning movements which allows for sections in the tank whichare difficult to access, e.g. in that the speed is reduced in specialzones to ensure cleaning of these zones.

If the inductor 9 of the hysteresis coupling is equipped with permanentmagnets, a maintenance-free coupling is achieved, which is relativelyinexpensive to manufacture, and which may be used in connection withinflammable and explosive liquids and vapours.

1. A cleaning head for mounting inside a tank, said cleaning headcomprising: a turbine which is driven by a source of pressure liquid forcausing rotation, a gear being driven by said turbine, said gear,causing a gear housing and a hub, mounted thereon and having nozzles, torotate, said liquid being conveyed from the turbine to the nozzles, saidgear housing being mounted on a stationary mounting part so that theliquid from the turbine bypasses the gear housing and flows to thenozzles, and a magnetic coupling for transferring the rotation of theturbine to an input shaft of the gear, the magnetic coupling havingcoupling parts, a driving coupling part disposed outside the gearhousing, and a driven coupling part disposed inside the gear housing,rotation of the turbine (3) being transferred to the gear in the gearhousing (13) via a hysteresis coupling comprising a magnetic inductor(9) disposed in a liquid space in which the turbine (3) is driven, themagnetic inductor (9) magnetically driving a hysteresis part (11) whichis mounted in the gear housing (13), and which is connected with theinput shaft (12) of the gear.
 2. A cleaning head according to claim 1,characterized in that the inductor part (9) is formed by electromagnets.3. A cleaning head according to claim 2, characterized in that theinductor part (9) has an adjustable magnetic field strength to adjust atorque or speed transferred by the hysteresis coupling.
 4. A cleaninghead according to claim 1, characterized in that the inductor part (9)is formed by permanent magnets.